This invention relates to blends of copolyetherester elastomers with nitrile copolymers, i.e., butadiene /acrylonitrile copolymers.
It is known to prepare thermoplastic elastomeric copolyetheresters, which are substantial linear, by reacting together a mixture of a dicarboxylic acid (or its ester), a long chain polymeric glycol, and a low molecular weight diol in suitable proportions. The product is a segmented block copolyetherester composed both of long chain ester units, which are those segments of the polymer chain derived from the esterification of the long chain glycol with the dicarboxylic acid, and short chain ester units derived from the esterification of the low molecular weight diol with the dicarboxylic acid. In a specific embodiment copolyetherester elastomers are prepared by copolymerization of dimethyl terephthalate (DMT), butanediol, and poly(tetramethylene ether)glycol (PTMEG). The polyester units of DMT and butanediol form a high-melting hard segment in the block copolyetherester, while the long chain ester units provide high elongation to the segmented copolyetherester. Representative copolyetheresters and their methods of preparation are disclosed in U.S. Pat. Nos. 3,651,014, 3,766,146, and 3,763,109.
These copolyetheresters are prepared by known procedures and provide elastomers having good tensile strength, tear strength and abrasion resistance, but they have not been found particularly suitable for application in blow-molding techniques due to instability of the parison, i.e., the extrudate suspended in the mold prior to blow-molding. Accordingly there has existed a need to improve the stability of these copolyetheresters on the parison without in any way detracting from the strength of the final blow-molded product.